Boeing has shown airlines a blueprint for the world’s longest-range passenger jet, adding spice to a long-awaited revamp of its 777 wide-body jet, people familiar with the matter said.

Boeing on Wednesday launched a race against Airbus for sales of the newest long-haul jets by announcing it had begun selling an upgraded aircraft family code-named 777X.

First seen in the 1990s, the 777 cornered the market for large twin-engine aircraft able to fly routes previously only possible with four engines, earning it the nickname “mini-jumbo.”

Analysts say the 777 is Boeing’s most profitable plane, thanks largely to the 777-300ER, a 365-seat version that began operations in 2004.

Most of the industry’s attention is now focused on a future 400-seat version known as the 777-9X, which is Boeing Co’s response to a growing challenge from the largest version of Europe’s newest aircraft, the Airbus A350-1000.

But talks between Boeing and potential buyers have also generated interest in a 777-8X that would be a successor to the 777-200LR, the industry’s current distance champion, with a range of more than 9,300 nautical miles, people briefed on the talks said.

The 777-8X, boasting a range of 9,500 nautical miles, would be designed for some of the world’s longest trips such as from the Middle East to South America.

“They are offering an ultra-long range aircraft in the 777-8X,” said an industry source briefed on the plans. “It’ll be the longest range aircraft in the business.”

Boeing declined to comment on specifics, but spokeswoman Karen Crabtree said the company is working with customers to fine tune the details.

Experts say ultra-long range planes deliver mixed benefits to airlines and so far the market for them remains a niche, overshadowed by the juggernauts designed for trunk routes.

That is because when modern aircraft fly the longest 15-hour flights, the first few hours are spent mostly burning the fuel needed to carry even more fuel for the rest of the flight.

These aircraft “carry more fuel to carry more fuel,” said consultant Richard Aboulafia of Virginia-based Teal Group.

“They need a very big wing with lots of (fuel storage) capacity, which means lots of structure and weight.”

Fuel is not the only source of extra weight. The long journey times also mean loading extra meals and a reserve crew, so that the fuel burned per hour – a measure of efficiency – can end up greater than if the plane simply stopped en route.

Airlines must balance this against any extra revenue they can charge for a direct flight and the ability to eliminate the fuel wasted in climbing and descending twice, as well as en-route landing fees and other costs linked to a stopover.

Niche market

Proof that ultra-long haul is not for everyone is contained in a quick comparison of sales for comparable existing models.

Boeing has sold 59 of its 777-200LR endurance jet, which entered service in 2007, compared with 687 of the shorter-range but highly popular 777-300ER.

Air India has announced plans to sell 5 777-200LR’s and one industry source said some or all could end up being acquired by the government for VIP transport. Air India declined comment.

Before the 777-200LR, the industry’s previous long-distance record-holder, the Airbus A340-500, was capable of flying 9,000 nautical mile on polar routes yet notched up fewer than 40 sales.

Production was halted in 2011, driven also by a wider slowdown in sales for all but the largest four-engine aircraft.

Reflecting thinner demand for super-long haul, the 777-8X is expected to take a backseat to the 777-9X, which is seen as the main weapon in an all-out defense of Boeing’s mini-jumbo franchise. The main model is slated to enter service at the end of the decade.

Nonetheless, recent public presentations suggest Boeing is confident the significantly enlarged wing and more powerful engines designed for the main 777-9X model will give airlines the flexibility to use the 777-8X spin-off more efficiently.

Randy Tinseth, vice president of Boeing marketing, told financiers in January the 777X would have “significantly lower operating cost” and greater payload and range ability. Airbus says its 350-seater is the right size and costs less to run.

As both sides trot out competing claims, the 777 vs A350 contest is likely to spark a fierce debate on technology – just as the industry digests the lessons of recent technical troubles on the 787 Dreamliner and, before that, the A380 superjumbo.

Boeing is expected to argue that its decision to keep the 777’s metal fuselage and focus on new carbon-fiber wings will marry increased performance with a proven record of reliability.

Airbus argues its A350-1000, the largest variant of its A350 family, will be cheaper to run because the whole plane, not just the wings, will be mainly built of lightweight carbon fiber.

Ironically, the two rivals are taking roughly opposite positions at the smaller end of the market for wide-bodied jets, where Boeing is pushing a possible all-composite stretched version of its 787 Dreamliner against the traditional A330, an older plane marketed on reliability and availability.

Both the 777 and A330 are important cash cows, helping to produce the funds needed to pay for ground-breaking developments such as the 787 and A350.